LOCK-UP AND REGISTRATION RIGHTS AGREEMENT BY AND AMONG BOSTON PROPERTIES, INC., BOSTON PROPERTIES LIMITED PARTNERSHIP AND THE HOLDERS NAMED HEREIN July 29, 2005

Exhibit 99.3

LOCK-UP AND REGISTRATION RIGHTS AGREEMENT

BY AND AMONG

BOSTON PROPERTIES, INC., BOSTON PROPERTIES LIMITED PARTNERSHIP

AND

THE HOLDERS NAMED HEREIN

July 29, 2005

TABLE OF CONTENTS

(i)

LOCK-UP AND REGISTRATION RIGHTS AGREEMENT

This Lock-up and Registration Rights Agreement (this “ Agreement ”) is entered into as of July 29, 2005 by and among Boston Properties, Inc., a Delaware corporation (the “ Company ”), Boston Properties Limited Partnership, a Delaware limited partnership (the “ Partnership ”), and the Persons named on Schedule A hereto (each a “ Holder ” and, if more than one, collectively, the “ Holders ”).

WHEREAS, Altid Enterprises, LLC, a New Hampshire limited liability company (“ Altid ”), being the successor by consolidation to Altid Enterprises Limited Partnership, a Massachusetts limited partnership, is a party to a Contribution Agreement dated as of October 20, 1999, by and among the Partnership, Altid, and the Trustees (as defined therein), as amended by Amendment No. 1 to Contribution Agreement, dated as of January 28, 2000 (the “ Contribution Agreement ”), relating to certain real property, in exchange for common units of limited partnership in the Partnership (“ Units ”);

WHEREAS, the Partnership, pursuant to its obligations under the Contribution Agreement, (i) issued 82,215 Units to Altid pursuant to an amendment to the Second Amended and Restated Agreement of Limited Partnership of the Partnership (as amended, the “ Partnership Agreement ”) dated as of June 19, 2000, (ii) issued an additional 18,445.78 Units to Altid pursuant to an amendment to the Partnership Agreement dated as of May 29, 2002 and (iii) issued an additional 21,675.10 Units (the “ Additional Units ”) to Altid pursuant to an amendment to the Partnership Agreement dated as of the date hereof;

WHEREAS, the Additional Units are being issued to the Holder in a private placement transaction and accordingly constitute restricted securities;

WHEREAS, upon the presentation of Additional Units to the Partnership for redemption in accordance with the terms hereof and the terms of the Second Amended and Restated Agreement of Limited Partnership of the Partnership (as amended, the “ Partnership Agreement ”), the Additional Units may be acquired by the Company in exchange for shares of common stock of the Company, par value $.01 per share (“ Common Shares ”), and the Company has agreed to provide certain registration rights to the Holder in respect of such Common Shares, and the Holder has agreed to certain restrictions on the transferability and redemption of the Additional Units and such Common Shares; and

WHEREAS, it is a condition precedent under the Contribution Agreement provides that each of the Company, the Partnership and the Holder enter into this Agreement with respect to the Additional Units.

NOW, THEREFORE, in consideration of the foregoing, the mutual promises and agreements set forth herein, and other valuable consideration, the receipt and

sufficiency of which are hereby acknowledged, the parties hereto hereby agree as follows:

1. Certain Definitions . As used in this Agreement, in addition to the other terms defined herein, the following capitalized defined terms shall have the following meanings:

“Additional Units” shall have the meaning set forth in the recitals hereto.

“Affiliate” shall mean, with respect to any specified Person, any other Person who, directly or indirectly, controls, is controlled by, or is under common control with such specified Person, provided that, for purposes of this definition, “control” (including, with correlative meanings, the terms “controlled by” and “under common control with”), as used with respect to any Person, shall mean the possession, directly or indirectly, of the power to direct or cause the direction of the management and policies of such Person, whether through the ownership of voting securities or by agreement or otherwise.

“Agreement” shall have the meaning set forth in the preamble hereto.

“Common Shares” shall have the meaning set forth in the recitals hereto.

“Company” shall have the meaning set forth in the preamble hereto.

“Contribution Agreement” shall have the meaning set forth in the recitals hereto.

“Dispose of” shall have the meaning set forth in Section 2.

“Holder” shall have the meaning set forth in the preamble hereto.

“Indemnitee” shall have the meaning set forth in Section 6.

“Issuance Registration Statement” shall have the meaning set forth in Section 3(b).

“Lock-up Period” shall have the meaning set forth in Section 2.

“NASD” shall mean the National Association of Securities Dealers, Inc.

“Partnership” shall have the meaning set forth in the preamble hereto.

“Partnership Agreement” shall have the meaning set forth in the recitals hereto.

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“Person” shall mean an individual, partnership, corporation, limited liability company, trust, or unincorporated organization, or a government or agency or political subdivision thereof.

“Permitted Distributee” means a direct or indirect holder of equity interests in a Holder that is listed on Schedule B hereto and that has delivered to the Company an Investor Questionnaire (as defined in the Contribution Agreement).

“Prospectus” means the prospectus included in any Registration Statement (including, without limitation, a prospectus that discloses information previously omitted from a prospectus filed as part of an effective Registration Statement in reliance upon Rule 430A promulgated under the Securities Act), as amended or supplemented by any prospectus supplement, with respect to the terms of the offering of any portion of the Registrable Shares covered by such Registration Statement, and all other amendments and supplements to the prospectus, including post-effective amendments, and all material incorporated by reference or deemed to be incorporated by reference in such prospectus.

“Registrable Shares” (a) when used with respect to a Holder, shall mean the Shares of any Holder, excluding (i) Shares issued to such Holder pursuant to an Issuance Registration Statement so long as such Holder is not an Affiliate of the Company, (ii) Shares for which a Resale Registration Statement relating to the sale thereof shall have become effective under the Securities Act and which have been disposed of under such Resale Registration Statement, (iii) Shares sold pursuant to Rule 144 or (iv) Shares eligible for sale pursuant to Rule 144(k) (or any successor provision) and (b) when used without reference to a Holder, shall mean Registrable Shares of all Holders.

“Registration Expenses” shall mean any and all expenses incident to performance of or compliance with this Agreement, including, without limitation: (i) all SEC, stock exchange or NASD registration and filing fees; (ii) all fees and expenses incurred in connection with compliance with state securities or “blue sky” laws (including reasonable fees and disbursements of counsel in connection with “blue sky” qualification of any of the Registrable Shares and the preparation of a Blue Sky Memorandum) and compliance with the rules of the NASD; (iii) all expenses of any Persons in preparing or assisting in preparing, word processing, printing and distributing any Registration Statement, any Prospectus, certificates and other documents relating to the performance of and compliance with this Agreement; (iv) all fees and expenses incurred in connection with the listing, if any, of any of the Registrable Shares on any securities exchange or exchanges pursuant to Section 3(d) hereof, and (v) the fees and disbursements of counsel for the Company and of the independent public accountants of the Company, including the expenses of any special audit or “cold comfort” letters required by or incident to such performance and compliance. Registration Expenses shall specifically exclude underwriting discounts and commissions relating to the sale or disposition of Registrable Shares by a Holder, the fees and disbursements of counsel representing a Holder in

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connection therewith as provided in Section 5, and transfer taxes, if any, relating to the sale or disposition of Registrable Shares by a Holder, all of which shall be borne by such Holder in all cases.

“Registration Statement” shall mean any registration statement of the Company which covers the issuance or resale of any of the Registrable Shares on an appropriate form, and all amendments and supplements to such registration statement, including post-effective amendments, in each case including the Prospectus contained therein, all exhibits thereto and all materials incorporated by reference therein.

“Resale Registration Statement” shall have the meaning set forth in Section 3(a).

“Resale Shelf Registration Expiration Date” shall have the meaning set forth in Section 3(a).

“Rule 144” means Rule 144 (or any successor provision) under the Securities Act.

“SEC” shall mean the Securities and Exchange Commission.

“Securities Act” shall mean the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

“Shares” (a) when used with respect to a Holder, shall mean any Common Shares issued or to be issuable to such Holder upon redemption or in exchange for Additional Units held by such Holder, which Additional Units were acquired by such Holder pursuant to the Contribution Agreement and (b) when used without reference to a Holder, shall mean the Shares of all Holders.

“Suspension Event” shall have the meaning set forth in Section 8(b).

“Units” shall have the meaning set forth in the recitals hereto.

2. Lock-up Agreement . Each Holder hereby agrees that for a period of one year after the date on which the Additional Units are issued (the “ Lock-up Period ”), without the consent of the Company, it will not offer, pledge, sell, contract to sell, grant any options for the sale of, seek redemption of, or otherwise dispose of, directly or indirectly (collectively “ Dispose of ”), any Additional Units; provided , however , that each Holder may (i) Dispose of Additional Units to a Permitted Distributee, (ii) Dispose of Additional Units pursuant to a pledge, grant of security interest or other encumbrance effected in a bona fide transaction with an unrelated and unaffiliated pledgee if such pledgee agrees that it will under no circumstances foreclose with respect to such Additional Units until after the first anniversary of the date on which the Additional Units are issued, (iii) Dispose of Additional Units upon

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death of a Holder to such Holder’s estate, executor, administrator or personal representative or to such Holder’s beneficiaries pursuant to a devise or bequest or by laws of descent and distribution, and (iv) after the Lock-up Period, Dispose of Additional Units in accordance with the terms of the Partnership Agreement; and provided , further , that the transferor shall, at the request of the Company, provide evidence reasonably satisfactory to the Company that the transfer is exempt from the registration requirements of the Securities Act. If a Holder Disposes of Additional Units as described in this Section 2, such Additional Units shall remain subject to this Agreement and, as a condition of the validity of such disposition, the transferee shall be required to execute and deliver a counterpart of this Agreement dated as of the date hereof (except that a pledgee shall not be required to execute and deliver a counterpart of this Agreement until it forecloses upon such Additional Units). Thereafter, such transferee shall be deemed to be a Holder for purposes of this Agreement.

3. Registration .

(a) Filing of Resale Shelf Registration Statement . Subject to the conditions set forth in this Agreement, the Company shall cause to be filed a Registration Statement under Rule 415 under the Securities Act relating to the sale by any Holder of all of the Registrable Shares of such Holder or Holders in accordance with the terms hereof (the “ Resale Registration Statement ”), and shall commence, no later than the first anniversary of this Agreement, the preparation of such Resale Registration Statement, and shall use reasonable good faith efforts to cause such Resale Registration Statement to be declared effective by the SEC within 90 days following the first anniversary of the date of this Agreement. The Company agrees to use reasonable good faith efforts to keep the Resale Registration Statement, after its date of effectiveness, continuously effective with respect to the Registrable Shares of each Holder until the earlier of (a) the date on which the Holder no longer holds any Registrable Shares or (b) the date on which all of the Registrable Shares held by such Holder have become eligible for sale pursuant to Rule 144(k) (or any successor provision) (hereinafter referred to as the “ Resale Shelf Registration Expiration Date ”).

(b) Registration Statement Covering Issuance of Common Shares . In lieu of the registration rights set forth in Section 3(a) above, the Company may, in its sole discretion, prior to the first date upon which the Additional Units held by the Holders may be redeemed (or such other date as may be required under applicable provisions of the Securities Act) file a Registration Statement (the “ Issuance Registration Statement ”) under Rule 415 under the Securities Act relating to the issuance to the Holders of Common Shares upon the redemption of Additional Units or in exchange for Additional Units. Thereupon, the Company shall use reasonable good faith efforts to cause such Issuance Registration Statement to be declared effective by the SEC for all Common Shares covered thereby. The Company agrees to use reasonable good faith efforts to keep the Issuance 5 Registration Statement continuously effective until the date on which all Holders have redeemed or

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exchanged their Additional Units for Common Shares or cash. In the event that (i) the Company, despite its reasonable good faith efforts, is unable to cause such Issuance Registration Statement to be declared effective by the SEC within 90 days of the first anniversary of this Agreement or (except as otherwise permitted by Sections 8(b) and 9) is unable to keep such Issuance Registration Statement effective until the date on which each Holder has redeemed or exchanged such Holder’s Additional Units for Common Shares, or (ii) a Holder is or becomes an Affiliate of the Company